Tire pressure indicator



May 26, 1953 H. G. BENZ 2,639,585

TIRE PRESSURE INDICATOR Filed Feb. 2, 1951 1,9 21 45 '5! 25" -46 44 I I/l2 F 4 4 INVENTOR Herbert G Benz ATTORNEY Patented May 26, 1953 TIREPRESSURE INDICATOR Herbert G. Benz, St. Paul, Minn.; George W. Benz,executor of the estate of said Herbert G. Benz,

deceased Application February 2, 1951, Serial No. 209,009

My invention relates to an improvement in tire pressure indicator anddeals particularly with a type of indicator which acts to explode acartridge when tire pressure falls below a predetermined point.

Various types of tire pressure alarms have been devised. Certain ofthese devices contain a blank cartridge and a hammer arranged to explodethe cartridge when the tire pressure falls below a predetermined point.Difficulty is experienced in keeping these devices from operating at thewrong time, providing an inaccurate alarm. As the tire strikes anobstruction or passes over an uneven portion of the road, the pressurewithin the tire often fluctuates due to sudden shock. It is difiicult toprovide a trigger arrangement which will function equally at the desiredtime without producing false alarms from time to time. 4

An object of the present invention lies in the provision of a tirepressure indicator which is simple in form and yet which functionseffectively under normal conditions of operation. The device is soarranged that the hammer will not actuate under normal tire fluctuationsto provide a false alarm. Accordingly the specific arrangement disclosedappears more accurate than other arrangements with which I am familiar.

An object of the present invention lies in the provision of a tirepressure indicator which includes an explosive cartridge and a springurged hammer for actuating the cartridge and including a cord or tiemember which holds the hammer in inoperative position. The cord or tieis arranged in the path of movement of a plunger which is normally heldin one extreme position by tire pressure. A spring is provided forurging the plunger in the opposite direction, the spring being ofsufficient. tension to overcome a predetermined tire pressure. Thus whenthe tire pressure within the tire drops to a predetermined minimum thespring urges theplunger in a direction to cause the knife bladesup-ported thereby to cut the cord or tie and to release the hammer.

A feature of the present invention lies in the fact that the hammer isefiectively held in inoperative position until the plunger movessufficiently to cut the tie. Small fluctuations of the plunger make takeplace without endangering the cord. However, when the spring pressureovercomes the reduced tire pressure due to a leak in the tire, the knifeon the piston will out the cord and the cartridge will be exploded.

7 Claims. (Cl. 1 16--34) These and other objects and novel features ofmy invention will be more clearly and fully set forth in the followingspecification and claims.

In the drawings forming a part of my specification:

Figure 1 is a side elevation view of the device in readiness for use.

Figure 2 is a perspective view of the device.

Figure 3 is a side elevational view of the device illustrated in Figurel, the cover plate having been removed therefrom to illustrate theappearance of the interior of the device.

Figure 4 is a sectional view showing the relative location of the partsafter the cord has been cut and the hammer released.

Figure?) is a perspective view of a detail portion of the device.

The tire pressure indicator includes a housing I0 which is shown ingenerally rectangular form having a pair of spaced end walls II and [2,a. pair of side walls I3 and I4, and a base wall l5. The closure plateI6 is secured by cap screws or other similar means I! to the open sideof the enclosures parallel to the base panel Hi to: normally seal the.interior of the casing.

A tubular fitting I9 is screwed into the wall I3 of the casing It, thefastening structure being best illustrated in Figure 4. The fitting I9is provided with a passage 20 therethrough communicating with anenlarged axial chamber 21 near its lower end. The plug 23 is threadedinto an internally threaded enlarged diameter portion 24 of the fittingI9. The plug 23 acts to peripherally clamp in place a resilientdiaphragm 25 which acts as a seal between the chamber 2| of the fittingI0 and the plug 24. This diaphragm is capable of stretching sufficientlyto allow the device to function in the manner which will be laterdescribed.

A plunger 26 is slidably supported within the casing l0, one end of theplunger extending through an aperture 2'1 in the plug 23 for guidancethereby. The plunger 26' is provided with an axial socket 29 in the endthereof remote from the diaphragm 25. A spring 30 is provided in thesocket or aperture 29 and encircles a tube 3| having an enlarged end 28forming a shoulder larger thanthe outside diameter of the spring andagainst which the spring may hear. The tube is internally threaded toadmit an adjusting screw 32, the head of which bears against the base ofa socket 33 in the inside surface of the housing [0. By turning theadjusting screw counter-clockwise the tension on the spring 30 will beincreased, thereby increasing the resistance to air pressure against thediaphragm 25, enabling the device to operate on a high pressure tire. Byturning the adjusting screw clockwise, the resistance to air pressureagainst the diaphragm is lowered and the alarm may be effective on a lowpressure time.

The plunger 26 is provided with an enlarged head 34 thereupon which isprefereiily provided with a that side 35 aeng ageable against the easingwall 15 to hold the plunger from rotation. A knife blade 36 is removablyattached to the plunger head 34. This knife blade 35 forms the cuttingblade for cutting the flexible cordor tie holding the cartridge hammerinoperative position.

The casing wall 12 is provided with an internally extending hollow boss3.] which is internally threaded to accommodate an externally threadedthumb nut or bushing 39. This thumb nut 39 is provided with an axialbore 40 of proper diameter to accommodate explosive cartridge 4!. Thecartridge in is provided with an enlarged head :52 at one end thereofwhich is designed .to fit between a shoulder 33 on the end of the boss31 and the end of the thumb nut or bushing 39.. Thus the head of thecartridge is clamped in place holding the cartridge end directedoutwardly in the bore 49. When the cartridge explodes the force may passdirectly to atmosphere, causing a sharp report.

The hammer mechanism includes a generally U -shaped spring arm 44 whichis anchored at one end 135 to a supporting box 45 on the base panel 15of the housing, The other end 4-1 of the spring arm 44 supports ,apointed hammer element 4,9 which forms a firing when the hammer springsagainst the cartridge. spring arm As is normally held in inoperatiueposition by a loop or length of cord 5,0 is fastened at one end to ,ahook member .51 on the casing Wall 1.1 and connected at the other end toa suitable loop ,52 on the spring arm end 41.

In mounting the ,device upon a vehicle wheel. it is desirable {toposition .the device .on the wheel cl e to axis, with the hoseconnection 53 connecting the fittin 19 to the tire yalve stem andextending downwardly from the housing 1 0, and the cartridge pointingforwardly. When the tire is inflated is connected to the fitting 1.9,the plunger as is the position illustrated in Figure 3 of the drawings.The loop or cord 5.0 is next connected in place to hold the hammer .44in inoperative position and a cartridge is then inserted into positionwithin the thumb nut J39.

ll/hen the tire pressure within the the falls below vapredeterminedfigure which has been Set by the adjusting screw 32, theplunger 26 is urged downwardly .by the sp g .30, deflectin the diaphragm25. The cartridge .cannothe accidentally fired as long as the cord orloop remains attached and the plunger 21B is usually held by thediaphragm {and by air tire pressure with the knife blade 35 in spacedrelation ,to this cord. The .lmife blade 35 may move ,a substantialdistance without contacting the cord, thus allowing certain fluctuationsin tire pressure without injuring the cord.

When the tire pressure within the tire falls to a predetermined extent,the spring 130 urges the plunger downwardly until the knife blade 36engages the cord 50 and cuts the same. The knife blade 36 is usuallysufiiciently sharp to easily cut the cord and the cutting action issimplified because of the tautness of the cord. As soon as the cord iscut the spring arm 44 swings the firing pin 49 against the cartridge end42, exploding the cartridge and providing the desired :alarm.

in accordance with the patent statutes, I have described the principlesof construction and operation of my tire pressure alarm, and while Ihave endeavored to set forth the best embodiment thereof, i desire tohave it understood that obyious chan es may he made within the scope ofthe following claims without departing from the spirit of my invention.

I claim:

'1. A tire pressure alarm for use in conjunction witha tire valve stemincluding a casing designed for attachment to the valve stem, a springurged actuating member within said casing, an alarm member the path ofsaid actuating member adapted to be struck thereby, :a cord holdin saidactuating member in inoperative position, a chamber in said casingcommunicating with the alve stem and subiect to pressure therein, aplunger m ged in one Erection ,by spring pliessure and urged in theopposite direction by tire pressure in said chamber, ,and means carriedby the plunger for cutting said cord.

2. The structure described in claim 1 and in which the actuating membersupports aiiring pin and the alarm member constitutes a cartridgesupported by said casing in the path of movemen-t ot-said pin.

3. The structure described in claim 1 and in eluding a diaphragmbet-ween said chamber and said plunger and engaging the end of theplunger,

4. A tire pressure indicator including a casing. a cartridge supportedby said casin a hammer movably supported in said casing for movement aainst said cartridge, p ing means su ng sa d hammer against saidcartridge, a cord for holiding said hammer out of contact with saidCar.- tridge, a knife blade, and means sensitive to air tire pressuremoi/ably supporting said knife blade a direction to cut said cord upon adecrease in the pness-ure.

5. The structure described in claim 4 and m hich the means supportingthe knife .blade is spring urged in direction to force the knife bladeagainst .the cord and cut same.

6. The structure described in claim 4, in which the hammer comprises aner ly U-shaned springstrip.

7, The structure described in claim ,4 and in which the means movablysupportin the lmife blade comprises .a plunger urged in one direction bytire pressure and urged in the other direction by spring means.

HERBERT G. -,BEIIZ.

References Cited in the file of this patent UNIT-ED srsrns PATENTSNumber Name Date 583,543 Nelson June 1, 118917 128L274 Berry Oct. 1-5,1918 1,688,361 Bryan-t June 21, I927

